1. Technical Field
The present technology pertains generally to devices and methods of sealing small fissures or other leaks in pipe or duct systems, and more particularly to a remote sealing process that uses aerosolized sealant particles of a specific size range with surfaces that have a specific “tackiness retention” time or “temporal profile of tackiness” so the tack range of the outer surface of the particles diminishes over time and/or distance from the injection point.
2. Background
Delivery of combustable gases or liquids from the source to consumers is through a network of pipes, typically located below ground. Aging networks, which are normally made of cast iron or steel pipes, can develop small fissures or cracks in the pipe walls or joints. The appearance of these pin point leaks can be due to corrosion, pitting, improper installation, fatigue, joint-seal failure or mechanical damage from soil subsidance or heavy traffic.
Networks with porous pipes can allow gas to continuously escape over time creating potentially dangerous situations with gas accumulations and waste. According to 1988 estimates, approximately 1% of all natural gas used within the United States was lost to leaks in the gas transportation networks. The country's natural gas consumption in that same year was 18.1×1012 cubic feet. Today, that same gas consumption is 23×1012 cubic feet, and costs on the order of $6 per 1000 cubic feet. This translates to approximately $1.4 billion dollars worth of natural gas escaping the distribution system through leaks.
Since natural-gas pipelines are typically buried underground, they must be uncovered and accessed to conduct even minor repairs, which require tremendous manpower and resources. Given that many compressed-gas distribution systems run under paved roadways and under building foundations, access remains a large problem and may be an impossibility. Additionally, many urban areas have aging infrastructure in dire need of repairs. In some cases, these systems are over 100 years old, and leaking sections must be patched or removed by hand. Due to the high cost and invasive nature of these repairs, minor leakage is often left unrepaired for long periods of time, wasting energy in the form of lost natural gas as well as transport energy, and adding escaped natural gas to the atmosphere, increasing overall greenhouse-gas emissions. This is significant since natural gas has a greenhouse impact roughly 25 times that of CO2.
Operators of older cast iron and steel distribution systems are routinely challenged to manage system leakage in a cost effective manner. As assets reach the point that replacement is warranted, it becomes more cost effective to replace sections of pipe versus repairing leaks. Due to public safety or the time required to plan and coordinate pipe replacement, it is very common for utilities to expend significant amounts of money to repair leaks on pipes that will ultimately be replaced.
Repair of underground pipelines generally involves exposing the pipeline and replacing the leaking section of pipe or joint with a new section or joint. One alternative is to essentially shrink-wrap the joint from the outside, which still requires excavation. Moreover, it can be quite difficult to precisely determine the location of leaks within a network of pipes. Rather than close down the pipeline to replace pipes that do not leak or where the location of the leak is uncertain, the outside surfaces of pipes may be coated with a polymeric coating such as polyurethane or other material coating in an attempt to seal small fissures as a temporary remedy. This strategy also requires excavation.
It is also very difficult to seal leaks remotely in a cost-effective manner. This is particularly important for low and medium pressure pipes with a large number of joints between sections.
Accordingly, there is a need for a method of identifying and repairing leaks in pipeline networks that does not require excavation and does not require normal pipeline distribution to be interrupted for any significant amount of time. The present technology satisfies these needs and is a significant improvement in the art.